Increased working capacity with hyperoxia in humans

The purpose of the study was to examine the influence of oxygen-breathing on maximal oxygen uptake (VO2max) and submaximal endurance performance. Six young women and five men rode a cycle-ergometer while breathing compressed air (normoxia, NOX) or a 55% O2 in N2 mixture (hyperoxia, HOX). The VO2max increased significantly by 12% (P less than 0.01) with HOX in the women but not in the men (+4%; nonsignificant). Maximal heart rate was also increased with HOX in the women but not in the men. Endurance time during work to exhaustion at 80% of normoxic VO2max was 41% longer in HOX than in NOX (P less than 0.025) with no significant difference between the men and the women. The variation among individuals was large. The oxygen uptake and respiratory quotient were not different in the two endurance tests, but pulmonary ventilation (VE) and blood lactate concentration were lower in HOX than in NOX, especially during the latter part of the task. Plasma base deficit (BDpl) increased initially by 3.5 mmol.l-1 during HOX and then stabilized. In NOX, a continuous increase was seen and the change was more than twice as large. Relative to BDpl, VE was higher in HOX than in NOX indicating a more efficient ventilatory compensation of the metabolic acidosis. The reduced ventilatory demand and lower metabolic acidosis in HOX in combination with lower relative exercise intensity may have contributed to the longer time to exhaustion. However, the pattern of individual variation suggested that other mechanisms were also involved.     

Upstream migratory behaviour in landlocked Arctic charr

Synopsis Extensive upstream migration of landlocked Arctic charr during spring floods was recorded in several tributaries of an oligotrophic lake in north-west Sweden. Migration was confined to a period of about two weeks and residence in most creeks was of short duration. Only fish migrating to two small productive lakes remained in the new habitat over the summer. Repeated annual migrations were only recorded in the creek leading to these lakes and no straying was observed among repeat migrants. Water temperatures provided the primary cues for initiation and direction of migration, although an ability to detect productive habitats by odour was indicated. Creek size, feeding opportunities during migration and conspeeific odour were subordinate guiding factors.     

Complementarity of genes for resistance to greenbug [Schizaphis graminum (Rondani)], biotype E,in sorghum [Sorghum bicolor (L.) Moench]

Summary Gene complementarity among various sources of resistance to greenbug biotype E was assessed. Analysis of the F₂ generation of crosses between susceptible and resistant parents (mating 1) and among sources of resistance (mating 2) suggested that resistance in sorghum to greenbug biotype E was complexly inherited and, to some extent, dependent on the nature of both the resistant and susceptible parents. Positive transgressive segregation in the F₂ generations of both matings was found to be due to effective plus factors, contributed by both parents in a cross, which complemented each other. The number of plus factors ranged from one to two in the susceptible parents and from two to five in the resistant parents of mating 1, and from one to five in the parents of mating 2. The consistently significant reciprocal effects shown by Sarvasi and PI264453 indicated that these sources had major factors for resistance in their cytoplasms, which were expressed in all their crosses. The results from this study indicated that the sources of resistance complemented each other to give increased number of F₂ segregates with increased resistance. Thus, it should be possible to increase and diversify resistance of sorghum to greenbug biotype E by accumulating different, effective plus factors from various sources through recurrent selection.Contribution No. 90-106-J from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan, KS 66506, USA     

Spatial and temporal localization of FGF receptors in Xenopus laevis

Summary Mesoderm formation is a result of cell-cell interactions between the vegetal and animal hemisphere and is thought to be mediated by inducing peptide growth factors including members of the FGF and TGF superfamilies. Our immunochemical study analyses the distribution of FGF receptors coded by the human flg gene during embryogenesis of Xenopus laevis. Immunostaining was detected in the dorsal and ventral ectoderm and also in the marginal zone of early cleavage, blastula and gastrula stages. Signals were very strong in the mid and late blastula (stage 8 and 9) and declined slightly in the early gastrula (stage 10). A dramatic decrease was observed up to the late gastrula (stage 11⁺). In stage 13 embryos, immunostaining was only found in cells around the blastopore. Isolated ectoderm cultured in vitro showed a similar temporal expression and decrease of the signal as the normal embryos. These results indicate that receptor expression is independent of the interaction of the animal cells with the vegetal part of the embryo. Of interest is the fact that the signal cannot only be found at or near the cell surface but also within the cell. This suggests the presence of an intracellular isoform of the receptor resulting from the endogenous expression of splice variants and the internalization of transmembrane receptor. Taken together our results suggest that the loss of competence (for bFGF around stage 10) is not directly correlated with the presence of receptors. The possible roles of heparan sulphate glucosaminoglycans (low affinity receptors) and control mechanisms in the intracellular signalling pathway downstream of the receptor level should be taken into consideration.     

人体和动物模型的体表物理信息地形图的研究

对人体头面、躯干、四肢、耳廓各局部几十个及整个人体等体表部位正、背面等210个部位进行超微弱冷光和温度测量,输入电子计算机,经特殊的自编程序处理,获得十分清晰的,由3000多数据构成的各个局部或人体整体的冷光和温度地形图。 对家兔左、右耳廓、胸腹部、背部都分别观察32个部位的冷光与体表温度,经计算机分析处理,每观察区域获得约由2000个数据构成的精确的冷光、温度地形分市图。并可见不同生理、病理状态及不同病程家兔体表冷光、温度等地形图呈有规律的改变。 此外,我们还编制了以体表左右相应对称部位差值为分析数据进行地形图分析的程序,用以人体和动物体表物理信息对称规律的研究。 本工作以图形的形式显示物理参量在体表的广泛的分布规律,以揭示机体内部的不同生理、病理状态。本方法定位准确、直观醒目,为研究体表信息及机体生命活动规律提供了与逐点直接测量方法相互补充的有益的新手段。     

Dichogamy,gender variation and bet-hedging inPseudowintera colorata

Summary Temporal patterns of variability in the longevity of the male and female phases of individual flowers and in the gender expression of plants of a dichogamous New Zealand tree,Pseudowintera colorata (Winteraceae), were documented in field studies. Two measures for the duration of phases in a dichogamous flower are distinguished; the nominal phases based on morphological features of the flower, and the effective phases reflecting the duration of their functions. Flower and phase longevity and phenotypic gender varied considerably throughout the season and among individuals. Temporal variability in phenotypic gender was loosely synchronized among the 12 plants sampled. Three effects of an environmental factor (temperature) were noted. First, increased temperatures shortened the duration of the female phase but had no effect on the duration of the male phase. Second, pollination frequency was positively correlated with temperature. These results indirectly suggest that increased pollination may shorten the duration of the female phase. Third, average population maleness, measured as the proportion of open flowers in the population on a given day which were in the male phase, was positively correlated with temperature. It is postulated that temperature indirectly influences temporal patterns of gender expression in the population through its differential effects on the longevity of the male and female phases in individual flowers. A theoretical model of bet-hedging shows that, if the direction of an environmental effect on the proportions of the sexual phases is irreversible, selection favours asynchronous dichogamy and reduces the temporal variability as much as possible. If the direction of the response is reversible, heterodichogamy is favoured.     

Effect of lowered muscle temperature on the physiological response to exercise in men

The effect of low muscle temperature on the response to dynamic exercise was studied in six healthy men who performed 42 min of exercise on a cycle ergometer at an intensity of 70% of their maximal O2 uptake. Experiments were performed under control conditions, i.e. from rest at room temperature, and following 45 min standing with legs immersed in a water bath at 12 degrees C. The water bath reduced quadriceps muscle temperature (at 3 cm depth) from 36.4 (SD 0.5) degrees C to 30.5 (SD 1.7) degrees C. Following cooling, exercise heart rate was initially lower, the mean difference ranged from 13 (SD 4) beats.min-1 after 6 min of exercise, to 4 (SD 2) beats.min-1 after 24 min of exercise. Steady-state oxygen uptake was consistently higher (0.2 l.min-1). However, no difference could be discerned in the kinetics of oxygen uptake at the onset of exercise. During exercise after cooling a significantly higher peak value was found for the blood lactate concentration compared to that under control conditions. The peak values were both reached after approximately 9 min of exercise. After 42 min of exercise the blood lactate concentrations did not differ significantly, indicating a faster rate of removal during exercise after cooling. We interpreted these observations as reflecting a relatively higher level of muscle hypoxia at the onset of exercise as a consequence of a cold-induced vasoconstriction. The elevated steady-state oxygen uptake may in part have been accounted for by the energetic costs of removal of the extra lactate released into the blood consequent upon initial tissue hypoxia.     

Morphology of the granular hemocytes of the Japanese horseshoe crabTachypleus tridentatus and immunocytochemical localization of clotting factors and antimicrobial substances

Summary The structure of hemocytes in the normal state and during blood coagulation, and the intracellular localization of three clotting factors and two antimicrobial factors were examined in the Japanese horseshoe crabTachypleus tridentatus. Two types of hemocytes were found in the circulating blood: non-granular and granular hemocytes. The latter contained numerous dense granules classed into two major types: L- and D-granules. The L-granules were larger (up to 1.5 m in diameter) and less electron-dense than the D-granules (less than 0.6 m in diameter). The L-granules contained three clotting factors and one antimicrobial factor, whereas the D-granules exclusively contained the other antimicrobial factor. After treatment with endotoxin, the L-granules were released more rapidly than the D-granules, although almost all granules were finally exocytosed. The granular hemocyte possessed a single Golgi complex; possible precursor granules of L-granules and D-granules contained tubular and condensed dense material, respectively. These data are discussed in relation to the self-defense mechanisms of the horseshoe crab.